Read the explanation above and if you don't understand it, try it for t < 0, where x = t^2 - 2. You will see all your values tend to -2 or go further away from it. The smaller t is the further away it is from -2 (it is larger than it) and the greater it is when it is negative so e.g. -4, -3, -2, -1 ... (or closer to 0) the closer it is to -2, but it will never reach -2 except t = 0. So, you will be able to conclude: when t < 0, x > -2.